Adrenergics - Catecholamines Flashcards
Name the Catecholamines (6).
Norepinephrine, Epinephrine, Isoproterenol, Dopamine, Dobutamine, Methyldopa
Norepinephrine. What receptors does it work on?
a1, a2, b1
Norepinephrine. Agonist or antagonist?
Agonist
Norepinephrine. What are its effects?
Peripheral vasoconstriction (a1 receptor), Increase BP (B1 and A1 receptor), no increase in HR b/c vagal reflex to decrease HR in presence of increased TPR and BP
Norepinephrine. Therapeutic uses (2).
Vasoconstrictor in intensive care situations
Elevate blood pressure during reduced sympathetic tone -> anesthesia, or neural injury
Epinepherine. What receptors does it work on?
A1, A2, B1, B2
Epinepherine. Agonist or antagonist?
Agonist
Epinephrine. What are its effects? CV, Respiratory, and Metabolic
CV - Increase HR, no net change in BP, slight decrease in PVR
Respiratory - Bronchodilation (B2 receptor)
Metabolic - gluconeogenesis, glycogenolysis, lipolysis, inhibit insulin release (b2 receptors)
Epinephrine. Explain the CV effects of this drug.
Increase in HR b/c of increase in contractile force and AV node conduction b/c direct stimulation of B1 Receptor.
No change in BP b/c increase in systolic but decrease in diastolic BP (b2 receptor)
Decrease in TVR b/c dilation of skeletal muscles via B2 receptor even with construction of other vessels via A receptors.
How is epinephrine administered?
Parentrally
Epinephrine. What receptor is most acted on?
B2
Explain the dose dependent CV effects of Epinephrine.
Moderate dose -> vasodilation b/c direct action of b2 receptors on skeletal muscle vessels -> dilation
Higher dose -> vasoconstriction b/c b receptors are full so drug starts binding to a receptors causing vasoconstriction of all vessels
Epinephrine. Therapeutic uses (4)
Rapid relief of hypersensitivity
Opthalmic -> pupil dilation
With local anesthetics (vasoconstriction) to increase time of action
Bradyarrhythmias -> restore contractility/rhythm in pts with cardiac arrest
Isoproterenol. What receptors does it bind?
B1, B2
Isoproterenol. Agonist or antagonist?
Agonist
Isoproterenol. What are its effects. CV, Respiratory
CV - Decrease BP and TVR (b/c b2 receptor and vasodilation), increase HR b/c direct stimulation of B1 receptor AND feedback from dec. BP
Respiratory - bronchodilation
What are the therapeutic uses of isoproterenol?
In emergencies to stimulation HR during bradycardia or heart block.
Is dopamine an antagonist or agonist?
Agonist
What receptors does dopamine act one?
DA1, A1, B1
What are the CV effects of dopamine - low dose?, medium dose?, high dose?
Low dose - 0.5ug/kg -> acts in DA1 receptor to increase renal blood flow by dilating renal vasculature
Medium dose - 5-10ug/kg -> acts on B1 receptor to increase HR and contractility (increase CO)
High Dose - 10-20ug/kg -> acts on A1 receptor, vasoconstriction and increase TPR
What are the therapeutic uses for dopamine?
severe decompensated heart failure, shock
Is dobutamine an agonist or antagonist?
Mixed b/c racemic
What receptors does dobutamine act on? (-, +, Racemic)
(-) -> a1 agonist, b agonist
(+) -> a1 antagonist, b agonist
Racemic -> b1 agonist
What are the therapeutic effects of dobutamine?
Increase HR and contractility, minimal change in BP and TPR
What are the therapeutic uses of dobutamine? (2)
Short term treatment of cardiac decompensation
Cardiac stress testing -> stress the heart to do the testing of pt is unable to exercise
What is significantly unique about methyldopa?
Orally active prodrug
What receptor does methyldopa act on?
A2
Is methyldopa an agonist or antagonist?
agonist
What are the effects of methyldopa?
decrease peripheral R, decrease HR, decrease CO
What is the major therapeutic use of methyldopa?
HTN, especially gestational b/c been proven to be safe for baby
What are the side effects of methyldopa? (4)
Sedation, dry mouth, edema, rebound HTN with sudden discontinuation
Explain the mechanism of action of methyldopa?
a-methyldopa -> CNS nerve cell ->decarboxylated by acid decarbozylase now is a-methyldopamine -> to storage granules via transporter -> converted to a-methylnorepinepherine by dopamine hydrozylase -> released instead of NE and acts on a2 receptors IN CNS
What prevents methyldopa deradation by MAO? What is the significance of that clinically?
alpha methyl group prevents degradation -> reason it can be given orally, long half life